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 Introduction
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<H2> Introduction</H2>With distributed programming, you can build applications running 
on several machines that work together through a network 
to accomplish a task. The computation model described here 
is parallel programming with distributed memory. Local and remote 
programs communicate using a network protocol. The best-known 
and most widely-used of these is IP (Internet protocol)
and its TCP and UDP layers. Beginning with 
these low-level layers, many services are built on the 
client-server model, where a server waits for requests 
from different clients, processes those requests, and sends responses.
As an example, the HTTP protocol allows communication 
between Web browsers and Web servers. The distribution 
of tasks between clients and servers is suitable for many different 
software architectures.<BR>
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The Objective CAML language offers, through its <TT>Unix</TT> library,
various means of communication between programs. 
Sockets allow communication through the TCP/IP and 
UDP/IP protocols. This part of the <TT>Unix</TT> library 
has been ported to Windows. Because you can create 
``heavyweight'' processes with <TT>Unix.fork</TT> as well as 
lightweight processes with <TT>Thread.create</TT>, you can create 
servers that accept many requests at once. Finally, 
an important point when creating a new service is the definition 
of a protocol appropriate to the application.<BR>
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